Transitive references

[BillHiebert]

◦xproj you only need to declare top level dependencies and others are pulled in automatically
◦This also has an impact on the publish artifacts. csproj only pulls from referenced assemblies and has special logic to exclude assemblies which are not actually used in code.

[davkean]

We think the cost here is going to be in two places:

• MSBuild work to actually flow the references
• UI work in the ReferencesSubTreeProvider to show inherited dependencies (xproj shows them under the project that it was inherited from)

We think that the language service will basically get this for free if MSBuild raises them as normal <Reference/> and <ProjectReference>.